Wordpress: reduce to the max

functions.php

<?php

function wp_customize_admin_menu() {
  remove_menu_page( 'edit.php' );
  remove_menu_page( 'edit-comments.php' );
  remove_submenu_page( 'themes.php', 'theme-editor.php' );
  remove_submenu_page( 'plugins.php', 'plugin-editor.php' );
  remove_submenu_page( 'tools.php', 'tools.php' );
  remove_submenu_page( 'tools.php', 'import.php' );
  remove_submenu_page( 'options-general.php', 'options-discussion.php' );
}
add_action('admin_init', 'wp_customize_admin_menu' );

function wp_customize_default_meta_boxes() {
  remove_meta_box( 'authordiv', 'page', 'normal' );
  remove_meta_box( 'commentstatusdiv', 'page', 'normal' );
  remove_meta_box( 'commentsdiv', 'page', 'normal' );
  remove_meta_box( 'postexcerpt', 'page', 'normal' );
  remove_meta_box( 'slugdiv', 'page', 'normal' );
  remove_meta_box( 'trackbacksdiv', 'page', 'normal' );

  remove_meta_box( 'dashboard_quick_press', 'dashboard', 'normal' );
}
add_action('admin_init', 'wp_customize_default_meta_boxes' );

function wp_remove_admin_bar_links() {
    global $wp_admin_bar;
    $wp_admin_bar->remove_menu( 'comments' );
    $wp_admin_bar->remove_menu( 'new-user' );
}
add_action( 'wp_before_admin_bar_render', 'wp_remove_admin_bar_links' );

function wp_init() {
  add_theme_support( 'post-thumbnails' );
  remove_theme_support( 'comments' );

  remove_post_type_support( 'post', 'post-formats' );
  remove_post_type_support( 'post', 'custom-fields' );
  remove_post_type_support( 'post', 'comments' );
  remove_post_type_support( 'post', 'author' );
  remove_post_type_support( 'post', 'trackbacks' );

  remove_post_type_support( 'page', 'custom-fields' );
  remove_post_type_support( 'page', 'comments' );
  remove_post_type_support( 'page', 'author' );
  remove_post_type_support( 'page', 'trackbacks' );
  add_post_type_support( 'page', 'thumbnail' );

  /* Remove 'subscriber' role */
  remove_role( 'subscriber' );

  remove_action( 'wp_head', 'wp_print_scripts' );
  remove_action( 'wp_head', 'wp_print_head_scripts', 9 );
  remove_action( 'wp_head', 'wp_enqueue_scripts', 1 );
  add_action( 'wp_footer', 'wp_print_scripts', 5 );
  add_action( 'wp_footer', 'wp_enqueue_scripts', 5 );
  add_action( 'wp_footer', 'wp_print_head_scripts', 5 );

  /* Remove feed links from head section */
  remove_action( 'wp_head', 'feed_links_extra', 3 );
  remove_action( 'wp_head', 'feed_links', 2 );
  remove_action( 'wp_head', 'rsd_link' );
  remove_action( 'wp_head', 'wp_resource_hints', 2 );
  remove_action( 'wp_head', 'rest_output_link_wp_head', 10 );
  remove_action( 'wp_head', 'wp_oembed_add_discovery_links', 10 );
  remove_action( 'wp_head', 'wlwmanifest_link');
  remove_action( 'wp_head', 'wp_shortlink_wp_head');
  remove_action( 'wp_head', 'wp_generator' );
  remove_action( 'wp_head', 'print_emoji_detection_script', 7 );
  remove_action( 'wp_print_styles', 'print_emoji_styles' );
}
add_action( 'init', 'wp_init' );

add_filter('rest_enabled', '__return_false');
add_filter('rest_jsonp_enabled', '__return_false');

add_filter('jpeg_quality', create_function( '', 'return 85;' ) );

function wp_disable_feed() {
  wp_die();
}
add_action('do_feed', 'wp_disable_feed', 1);
add_action('do_feed_rdf', 'wp_disable_feed', 1);
add_action('do_feed_rss', 'wp_disable_feed', 1);
add_action('do_feed_rss2', 'wp_disable_feed', 1);
add_action('do_feed_atom', 'wp_disable_feed', 1);

function wp_enqueue_scripts() {
  if ( !is_admin() ) {
    wp_deregister_script( 'jquery' );
  }

  wp_enqueue_script(
    'jquery',
    get_template_directory_uri() . '/assets/javascripts/jquery.min.js'
  );

}
add_action( 'wp_enqueue_scripts', 'wp_enqueue_scripts' );

function wp_customice_tiny_mce( $in ) {
  $in['paste_remove_styles'] = true;
  $in['paste_remove_spans'] = true;
  $in['apply_source_formatting'] = false;
  $in['block_formats'] = "Paragraph=p; Heading 1=h1; Heading 2=h2; Heading 3=h3";
  $in['toolbar1'] = 'formatselect,bullist,numlist,bold,italic,underline,strikethrough,alignleft,aligncenter,alignright,alignjustify,link,unlink,charmap,undo,redo,wp_help ';
  $in['toolbar2'] = '';
  $in['toolbar3'] = '';
  $in['toolbar4'] = '';
  return $in;
}
add_filter( 'tiny_mce_before_init', 'wp_customice_tiny_mce' );

// Disable emojis
function disable_emojis() {
 remove_action( 'wp_head', 'print_emoji_detection_script', 7 );
 remove_action( 'admin_print_scripts', 'print_emoji_detection_script' );
 remove_action( 'wp_print_styles', 'print_emoji_styles' );
 remove_action( 'admin_print_styles', 'print_emoji_styles' ); 
 remove_filter( 'the_content_feed', 'wp_staticize_emoji' );
 remove_filter( 'comment_text_rss', 'wp_staticize_emoji' ); 
 remove_filter( 'wp_mail', 'wp_staticize_emoji_for_email' );
 add_filter( 'tiny_mce_plugins', 'disable_emojis_tinymce' );
 add_filter( 'wp_resource_hints', 'disable_emojis_remove_dns_prefetch', 10, 2 );
}
add_action( 'init', 'disable_emojis' );

/**
 * Filter function used to remove the tinymce emoji plugin.
 * 
 * @param array $plugins 
 * @return array Difference betwen the two arrays
 */
function disable_emojis_tinymce( $plugins ) {
 if ( is_array( $plugins ) ) {
 return array_diff( $plugins, array( 'wpemoji' ) );
 } else {
 return array();
 }
}

/**
 * Remove emoji CDN hostname from DNS prefetching hints.
 *
 * @param array $urls URLs to print for resource hints.
 * @param string $relation_type The relation type the URLs are printed for.
 * @return array Difference betwen the two arrays.
 */
function disable_emojis_remove_dns_prefetch( $urls, $relation_type ) {
 if ( 'dns-prefetch' == $relation_type ) {
 /** This filter is documented in wp-includes/formatting.php */
 $emoji_svg_url = apply_filters( 'emoji_svg_url', 'https://s.w.org/images/core/emoji/2/svg/' );

$urls = array_diff( $urls, array( $emoji_svg_url ) );
 }

return $urls;
}

// disable embedding posts from other people's blogs/websites
function my_deregister_scripts(){
  wp_deregister_script( 'wp-embed' );
}

add_action( 'wp_footer', 'my_deregister_scripts' );
// disable displaying login errors
add_filter( 'login_errors', create_function( '$a', "return null;" ) );

?>